Purpose: To collect and look at particulate matter that is in polluted air.
Particulates are small solid particles and liquid droplets that are suspended in the air. Collectively, these particulates are called aerosols. Natural sources of particulates include dust, volcanic ash, and pollen. The dispersal of airborne particulates in the atmosphere because of human activity has become a concern because of health related problems to living things. Human sources of particulates include dust from plowing and overgrazing of arid land, mineral dust from mining and smelting, coal and oil burning power plants, ash and smoke from industries, vehicles, particularly those that burn diesel fuel, and burning wood in fireplaces and wood-burning stoves. Liquid particulates include sulfuric acid, PCBs, petroleum, and pesticides. Industrial processes account for 40% of the 6.6 million metric tons emitted in the United States each year. Cars account for 17% of the particulates.
Particulate sizes are measured in microns. A micron is one-millionth of a meter, which is also one-thousandth of a millimeter. "Fine dust" is less than 100 microns in diameter, "coarse dust" or "grit" is greater than 100 microns, and "fumes" are between 0.0001 to 1 micron in size. Small particulates, .1 micron (0.001 mm), can remain in the atmosphere for several months or even years. Winds can carry the particulates thousands of miles. Rain and snow help to clear particulate matter from the atmosphere.
Particulate air pollutants can be harmful to human and animal life if inhaled. Our body naturally can filter out large particulates with the hair in our nose, mucus in our throat, and cilia in our lungs. Small particulates can carry poisonous substances into our lungs and cause breathing problems and lung damage.
Observation of Particulates
Materials: Flashlight or slide projector.
Tap a chalk board eraser below the light to show how the dust is suspended in the air. Turn the lights on while there is a large amount of "dust" visible in the light beam. Notice the particulates are less visible in the increased light.
Summarize what you learned about particulates--where are they, what do you think causes them, and how abundant are they?
Collecting and Observing Particles in the Air
Materials: Posterboard or thin cardboard, scissors, ruler, transparent tape, string, hole punch, magnifying glass or dissecting microscope, analytic balance.
Analysis (answer on a sheet of paper)
Are there differences in the particles based on where the air strips were placed?
Which collectors had the most particulates and why?
What variables or conditions might affect the amount of particulates collected on a collector?
What are some health hazards associated with the particulates you collected?
How could particulate pollutants dispersed by human activity be reduced?